Increasing lower engine emission standards call for increasingly more sophisticated engine controls. On way to improve engine operation is to install pressure sensors in engine cylinders. The pressure sensors may provide feedback that may be indicative of engine combustion for combustion location, combustion amount, quality, engine performance, durability and engine emissions for each of the cylinders that a pressure sensor is installed in and the engine itself. A pressure sensor may be installed in each engine cylinder so that a controller may evaluate the way the cylinder is operating. For example, if any of the mass fraction burn locations for an individual cylinder is delayed longer than is desired, engine fuel injection timing of that cylinder may be advanced to advance the crankshaft location of the mass fraction burn location during an engine cycle for the particular cylinder. Thus, cylinder pressure sensors may provide important and useful feedback of cylinder combustion and operation. However, installing a pressure sensor in each engine cylinder may increase engine cost and the amount of computational computing power that a controller may have to provide to process the cylinder pressure sensor data. Therefore, it would be desirable to be able to control the combustion process in each engine cylinder without having to cover the cost of installing a pressure sensor in each engine cylinder.
The inventors herein have recognized the above-mentioned disadvantages and have developed an engine operating method, comprising: evaluating operation of a plurality of engine cylinders for two or more engine cylinders by comparing the crankshaft signals between the indicated and non-indicated cylinders, but less than the plurality of engine cylinders, that provide lowest root mean square error values based a parameter; and installing pressure sensors in two or more engine cylinders, but less than the plurality of engine cylinders, that provide the lowest root mean square error values based on the parameter.
By selectively installing pressure sensors into only a fraction of engine cylinders that provide a lowest root mean square error value of an engine parameter based on pressure sensor output from the cylinders, it may be possible to provide the technical result of improving combustion in an engine without having to install a pressure sensor in each engine cylinder. Further, by installing pressure sensors in more than one engine cylinder, but in less that all engine cylinders, it may be possible to improve combustion by a greater extent for all the cylinders over the entire operating map than if only a single cylinder pressure sensor is installed in an engine. Specifically, two engine cylinder pressure sensors located in two different engine cylinders and that provide lowest root mean square error values for an engine parameter may be a basis for controlling combustion in all engine cylinders. For example, a pressure sensor positioned in cylinder number one of an engine and a pressure sensor located in cylinder number eight of the engine may provide lowest root mean square error values for determining engine torque at a plurality of engine speed and load conditions. The pressure sensors located in cylinder number one and eight may be the basis for modifying combustion in all engine cylinders over the engine operating range and expanding the operating range.
The present description may provide several advantages. For example, the approach may improve combustion in one or more engine cylinders. Further, the approach may reduce the cost of improving combustion in one or more engine cylinders. Further still, the approach may improve estimates of select engine control parameters by determining values of the engine control parameters based on pressure sensors that exhibit a higher signal to noise ratio.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.